Preheat your oven to 200°F (95°C). In a large mixing bowl, combine all-purpose flour, instant dry yeast, fine salt, and optional poppy seeds. Whisk together and set aside.

In a separate bowl, mix buttermilk, granulated sugar, and softened unsalted butter. Microwave for about 30-40 seconds until warm, then stir until well combined.

Gradually pour the buttermilk mixture into the dry ingredients while stirring gently. Add the eggs and fresh lemon zest, mixing until a sticky dough forms.

Sprinkle additional flour to the dough and knead gently until it pulls away from the sides of the bowl, reaching a tacky but not sticky consistency.

Cover with a towel and let the dough rest in a warm area for 10-20 minutes.

In a small bowl, mix light brown sugar and granulated sugar with the zest of one lemon, then blend in softened butter until smooth.

Roll out the dough into a 12"x18" rectangle, spread the filling mixture evenly, and roll into a log. Slice into 12 pieces using dental floss.

Place the rolls in a greased 9x13 inch pan, cover with foil, and let rise in a warm oven for 30 minutes.

Remove cover, preheat to 350°F (175°C), and bake for 28-32 minutes until golden brown.

For icing, whisk together powdered sugar, lemon juice, and melted butter until smooth.

Allow rolls to cool, then drizzle with icing and garnish with fresh lemon zest.